Biochemical binding assays have been widely utilized in recent years to determine the presence and the concentration of analytes in biological specimens. As known in the art, heterogeneous assays are those in which one of the reactive binding partners is bound to a solid-phase. The various types of heterogeneous assays include, for example, the sandwich method, the indirect method, and the competitive method.
As used herein, "binding partner" is defined to include a specific binding partner to the analyte, an analyte analogue, and the analyte. "Non-specific binding" is defined as non-specific interactions of the binding partners with a solid surface in an assay system.
The non-specific binding often reduces the sensitivity of the heterogeneous assays. The sensitivity of the assay typically refers to the smallest mass of analyte that generates a statistically significant change in the signal generated by the assay when compared to the signal reading obtained in the absence of the analyte. There is a need to develop methods to increase the sensitivity of binding assays (i.e. detect smaller amounts of analyte). Furthermore, a high sensitivity assay is typically capable of an overall higher precision measurement of the analytes.
A number of methods are known for reducing the non-specific binding in heterogeneous assays. For example, proteins such as, bovine serum albumin (BSA), gelatin, and casein, have been added to the assay reagents or preadsorbed on the solid-phase in order to block non-specific adsorption sites. Additionally, the use of various surfactants, often in high concentrations, has been reported in the literature.
While known techniques may assist in reducing some non-specific adsorption, many of the prior art techniques have been associated with interference of the desired specific interaction of the binding partners or lead to the displacement of the specific binding complex formed. Additionally, despite the use of high concentrations of protein and surfactant taught by the literature, a considerable amount of non-specific binding typically still exists in many heterogeneous assays. Alternative means to reducing non-specific binding in heterogeneous assays are needed.